1. Technical Field
The present invention relates to an electrostatic and piezoelectric touch panel.
2. Related Art
Keyboards and optical mice are the most common and widely used information input apparatuses designed for computers. However, due to the size and inconvenience of carrying such apparatuses, touch input devices, which can be stacked on screens, are developed as a replacement.
Touch panels are user-friendly input devices, which allow direct input of a command by using a finger or stylus to touch a specific region on the panels. The trending demand of most electronic products is the need to be light, thin, short, small, and capable. Although such requirements cause available space in electronic products to become more and more constrained, touch devices can be implemented so as to advantageously use less space. A touch device not only functions as a keyboard and an optical mouse, but also provides a handwriting data input function. Therefore, touch devices offer the best solution for a human-machine interface.
According to their operation principles, touch panels can be classified into four categories: resistive touchscreen panels, capacitive touchscreen panels, optical touchscreens, and surface wave touchscreen panels. Each category has one or more disadvantages. The resistive touchscreen panels have lower light transmittance and suffer from poorer contrast and low brightness. The capacitive touchscreen panels are easily affected by temperature, humidity, and grounding level, and have poor stability as a result. Moreover, the capacitive touchscreen panels need a conductor in order to operate; otherwise, the capacitive touchscreen panels cannot detect a contact. The resolutions of the optical touchscreens are determined by the number of infrared emitters or receivers and their resolutions are limited. The surface wave touchscreen panels use transmitting transducers to generate surface waves and receiving transducers to receive the surface waves. The position of a touch point is determined by using a diagram describing a relationship between received signal strength and time. U.S. Pat. No. 4,644,100 discloses a surface wave touchscreen using one transmitting transducer and one receiving transducer. However, because the speed of a surface wave is faster, a surface wave touchscreen needs a faster signal processor and a high performance analogue/digital converter such that the cost of a surface wave touchscreen is high. By attempting to reduce the cost, the resolution of the surface wave touchscreen has to be compromised.
The current touch panels have many problems. For example, each touch panel employs only one touchscreen technology. A capacitive touchscreen panel may detect contact when a finger does not touch the panel because of a cross-linking effect, leading to a touch false judgment.